A wide variety of commercially formulated foods for consumer consumption are prepared with a liquid dairy product, and very often where the liquid dairy product is in a concentrated form, e.g. ice cream, sour cream, white sauces, milk chocolate, salad dressings, and the like. In such commercially formulated foods, a concentrated dairy product is often used, since, otherwise, the excess water of, for example, skim milk or whole milk, must be removed from the formulation during processing into the finished product. This is because the total solids content of the dairy product ingredient or the finished formulated food must be relatively high, and to reach those higher total solids contents, at least some of the water of a natural state liquid dairy product must be removed.
Generally speaking, processes for increasing the solids contents of dairy products can be broadly classified into two categories, i.e. thermal processes and mass transfer processes. Thermal processes involve heating the liquid dairy product to a temperature where the non-solids of the dairy product are evaporated or distilled. Such processes can alter the solids content of the dairy product such that either a relatively highly concentrated dairy product or a dried dairy product is obtained. Typical thermal processes include heat evaporation, oven drying and spray drying.
Mass transfer concentration processes do not normally include a thermal process, or, at least, include a thermal process with substantially less thermal separation than typical thermal processes. Among known mass transfer processes are ultrafiltration, centrifugal separation and freeze drying.
One of the most common forms of concentrated dairy product is that of evaporated milk, either whole milk or reduced fat milk or skim milk. The process involves heating under vacuum and is, in part, therefore, a thermal process. Another common form of concentrated dairy product is the powdered form, achieved by spray drying, which, again, is a thermal process. Mass transfer processes are far less commonly used than thermal processes, since the thermal processes are easier to operate and considerably less inexpensive. However, one mass transfer process, i.e. ultrafiltration, has found applicability for concentrating liquid dairy products where it is desired, during the concentrating step, to remove other components of the liquid dairy product, e.g. ash and the like, in addition to water removal.
Accordingly, as a general statement, most of the concentrated dairy products are made by thermal processes, including vacuum pan evaporation, heat evaporation and spray drying. However, as is well known, these thermal processes, unfortunately, alter the taste, texture and mouth feel of the resulting concentrated product. For example, evaporated skim milk or whole milk has a taste, texture and mouth feel, either in the concentrated form or in the reconstituted form (reconstituted with water), which is substantially different from the taste, texture and mouth feel of the fresh milk. In addition, the functionality of the evaporated milk, as opposed to fresh milk, is changed during that thermal processing. For example, evaporated milk cannot be used in certain types of cooking and baking, as opposed to fresh milk, and evaporated whole milk, while having a fat content similar to cream, cannot be effectively whipped into a traditional whipped cream. On the other hand, as is also well known, spray dried skim milk or whole milk, when reconstituted with water, has a somewhat cooked taste, which is quite objectionable to large numbers of people.
Thus, as a practical matter, in formulated foods containing a concentrated dairy product, the art has, essentially, been restricted to evaporated or spray dried dairy products, i.e. in the concentrated, partially reconstituted or fully reconstituted form, but both of these introduce unwanted tastes, textures and mouth feel to the formulated foods. The general approach in the art in connection with the unwanted taste is to overpower that unwanted taste by the inclusion of relatively large amounts of the flavoring used in the formulated food. For example, in ice cream, evaporated milk and/or spray dried milk powder may be used, but, to mask unwanted flavors, the amount of the flavoring of the ice cream, e.g. vanilla, is considerably increased beyond that which would be necessary if the ice cream had been made from formulations which do not include a concentrated form of the dairy product, but instead include fresh skim or whole milk or cream.
However, the defects introduced into such formulated foods by conventional concentrated dairy products in terms of texture and mouth feel have never been adequately dealt with by the art, and these defects continue in such formulated foods. A notable example thereof is ice cream made with concentrated dairy products, where the undesired flavors thereof are masked by high proportions of flavoring materials, and the undesired texture and mouth feel are masked by use of relatively large amounts of gums and thickeners. While such gums and thickeners do mask the undesired mouth feel of such products, they also introduce other unwanted textures and mouth feels, and, therefore, the use of such gums and thickeners is a definite compromise in the art.
Similar problems exist with other foods formulated with concentrated dairy products, such as cultured foods, e.g. low fat or imitation sour cream or cream cheese, as well as cooked foods, e.g. white sauces and soups. The problem also exists in other formulated food mixtures using concentrated dairy products, e.g. milk chocolate and salad dressings. In these other various foods, the art has taken a number of different approaches to mitigate the undesired flavors, mouth feel and texture, but, here again, all of these approaches result in definite compromises, similar to the ones described above in connection with ice cream.
It would, of course, be of considerable advantage to the art to eliminate these difficulties with formulated foods containing concentrated dairy products, but, as noted above, all prior efforts in the art, using conventionally produced concentrated dairy products, produced less than desired results.
However, in commonly assigned U.S. Pat. No. 4,959 234 a method is disclosed for concentrating liquid dairy products, wherein that concentration is effected by a freeze concentration process. A freeze concentration process should be carefully distinguished from a freeze drying process, which is entirely different and produces a dried solid material, e.g. the process used for making freeze dried soluble coffee. In the patented process, a liquid dairy product is cooled to a temperature at or below its freezing point. Formed ice crystals are recrystallized from the cooled liquid dairy product to produce a mixture of concentrated product and ice crystals. A portion of the ice crystals is separated from the mixture and heated to form a melt. The mixture is washed with the melt to form a washed mixture of the concentrated product and the ice crystals. The ice crystals are separated from the washed mixture, and the concentrated product is recovered. That process is described in detail in that patent and will not be repeated herein, for sake of conciseness, and the entire disclosure of that patent is incorporated herein by reference.
That U.S. Pat. No. 4,959,234 goes on to disclose that the freeze concentrated liquid dairy products of that process have improved taste, texture and mouth feel, as opposed to the conventionally concentrated dairy products, either in the concentrated form or in the reconstituted form thereof, when the freeze concentration process is carried out to the extent that the freeze concentrated liquid dairy product has a solids content of at least 20%, and when the solids contents is at least about 30% or more, a very significant increase in the improvements of taste, texture and mouth feel is achieved. For example, when the freeze concentrated liquid dairy product is derived from skim milk, and the concentrated product is reconstituted with water to produce substantially the same solids content as that of the skim milk originally fed to the process, the taste is much more similar to reduced fat milk, e.g. 2% milk, than to skim milk. Further, the texture is far more creamy than skim milk, e.g., the texture is similar to whole milk. The mouth feel is not the watery mouth feel of skim milk, but has a mouth feel similar to reduced fat milk, e.g. 2% fat milk. In addition, that patent points out that freeze concentrated skim milk is whipable, as opposed to the unwhipable nature of evaporated milk.
Accordingly, that patent describes a new concentrated liquid dairy product, i.e. the described freeze concentrated liquid dairy product, which new product does not suffer from the difficulties described above in connection with taste, texture and mouth feel. It was, therefore, expected that the use of such freeze concentrated liquid dairy products in formulated foods should, at least in part, avoid the difficulties of those formulated foods when using conventionally concentrated dairy products, as described above.